Field of the Invention
The present invention relates to an image forming apparatus, and further to a lock mechanism of a drawer unit which is included in an image forming apparatus to store an article such as recording paper.
Description of the Related Art
An image forming apparatus, such as a printer and a multifunction peripheral (MFP) of a printer, includes a paper cassette for storing recording paper on which an image is formed. The paper cassette is detachably attached to a cassette storage unit included in an image forming apparatus body. According to this type of image forming apparatus, recording paper stored in the paper cassette is sequentially conveyed to an image forming unit to form an image on the recording paper thereat at the time of image formation.
The paper cassette of the image forming apparatus is drawn from the cassette storage unit for replenishment of recording paper. A lock mechanism is provided to prevent separation of the paper cassette from the cassette storage unit, which may be caused when the paper cassette is drawn from the cassette storage unit.
It is preferable to detach the paper cassette from the cassette storage unit at the time of maintenance of the image forming apparatus, for example, to increase work efficiency. Accordingly, a predetermined unlock operation is performed for the lock mechanism to detach the paper cassette from the cassette storage unit. There have been proposed, for example, a lock mechanism which performs an unlock operation for raising a tip of the paper cassette upward in a maximum drawn-out state of the paper cassette (JP 2012-126575 A), and a lock mechanism which performs an unlock operation for revolving (rotating) a lock member provided on aside surface of the paper cassette upward and downward (JP 11-301861 A).
The paper cassette is often disposed in a lower part of the image forming apparatus. In this case, force for raising the tip of the paper cassette may be added to the paper cassette as well as force for pulling the paper cassette when an operator performs a drawing operation for drawing the paper cassette. According to an image forming apparatus including the lock mechanism described in JP 2012-126575 A, therefore, the unlock operation may be unconsciously performed during the drawing operation in the maximum drawn state of the paper cassette. In this case, the paper cassette may drop during the action for drawing the paper cassette.
On the other hand, according to an image forming apparatus including the lock mechanism described in JP 11-301861 A, the lock member provided on the side surface of the paper cassette is operated to perform the unlock operation. In this case, an operator usually operates the lock member without visually recognizing the lock member. When the unlock operation is a revolving operation upward and downward, the operator may perform the unlock operation unintentionally while feeling for the lock member, and may drop the paper cassette.